Simultaneous determination of seven phthalic acid esters in beverages using ultrasound and vortex‐assisted dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography

A sensitive, rapid, and simple high‐performance liquid chromatography with UV detection method was developed for the simultaneous determination of seven phthalic acid esters (dimethyl phthalate, dipropyl phthalate, di‐n‐butyl phthalate, benzyl butyl phthalate, dicyclohexyl phthalate, di‐(2‐ethylhexyl) phthalate, and di‐n‐octyl phthalate) in several kinds of beverage samples. Ultrasound and vortex‐assisted dispersive liquid–liquid microextraction method was used. The separation was performed using an Intersil ODS‐3 column (C₁₈, 250 × 4.6 mm, 5.0 μm) and a gradient elution with a mobile phase consisting of MeOH/ACN (50:50) and 0.2 M KH₂PO₄ buffer. Analytes were detected by a UV detector at 230 nm. The developed method was validated in terms of linearity, limit of detection, limit of quantification, repeatability, accuracy, and recovery. Calibration equations and correlation coefficients (> 0.99) were calculated by least squares method with weighting factor. The limit of detection and quantification were in the range of 0.019–0.208 and 0.072–0.483 μg/L. The repeatability and intermediate precision were determined in terms of relative standard deviation to be within 0.03–3.93 and 0.02–4.74%, respectively. The accuracy was found to be in the range of –14.55 to 15.57% in terms of relative error. Seventeen different beverage samples in plastic bottles were successfully analyzed, and ten of them were found to be contaminated by different phthalic acid esters.     

Simultaneous determination of serum propafenone and its metabolites using high‐performance liquid chromatography

Propafenone, a class Ic antiarrhythmic agent, is metabolized to 5‐hydroxypropafeone (5‐OHP) and N‐depropylpropafenone (NDPP). Simultaneous determination of serum propafenone and its metabolites was performed using HPLC equipped with a conventional octadecylsilyl silica column and ultraviolet detector. The wavelength was set at 250 nm. Propafenone and its metabolites in the serum were extracted using diethyl ether. The mobile phase solution, comprising 1‐pentanesulfonic acid sodium salt (0.1 m ), acetonitrile and acetic acid (280:185:2.5, v/v/v), was pumped at a flow rate of 1 mL/min. The recoveries of propafenone, 5‐OHP and NDPP were greater than 85, 82 and 60%, respectively, with the coefficients of variation (CVs) less than 5.4, 1.9 and 2.9%, respectively. The calibration curves were linear for a concentration range of 12.5–1500 ng/mL for propafenone and 2–500 ng/mL for 5‐OHP and NDPP (r > 0.999). CVs in the intraday assays were 1.0–3.8% for propafenone, 0.6–2.0% for 5‐OHP and 0.6–1.7% for NDPP. CVs in interday assays were 1.3–7.7% for propafenone, 1.1–6.5% for 5‐OHP and 5.4–8.0% for NDPP. The present HPLC method can be used to assess the disposition of propafenone and its metabolites for pharmacokinetic studies and therapeutic drug monitoring of propafenone.     

Application of an optimized dispersive nanomaterial ultrasound‐assisted microextraction method for preconcentration of carbofuran and propoxur and their determination by high‐performance liquid chromatography with UV detection

An extraction method based on dispersive nanomaterial ultrasound‐assisted microextraction was used for the preconcentration of carbofuran and propoxur insecticides in water samples prior to high‐performance liquid chromatography with UV detection. ZnS:Ni nanoparticles were synthesized based on the reaction of the mixture of zinc acetate and nickel acetate with thioacetamide in aqueous media and then loaded on activated carbon (ZnS:Ni‐AC). Different methods were used for recognizing the properties of ZnS:Ni‐AC and then this nanomaterial was used for extraction of carbamate insecticide as new adsorbent. The influence of variables on the extraction method (such as amount of adsorbent (mg: NiZnS‐AC), pH and ionic strength of sample solution, vortex and ultrasonic time (min), ultrasound temperature and desorption volume (mL) was investigated by a screening 2^7–4 Plackett–Burman design. Then the significant variables were optimized by using a central composite design combined with a desirability function. At optimum conditions, this method had linear response >0.0060–10 μg/mL with detection limit 0.0015 μg/mL and relative standard deviations <5.0% (n = 3).     

Simultaneous determination of six herbal components in intestinal perfusate by high‐performance liquid chromatography

An effective, accurate and reliable HPLC with UV detection method was developed and validated for quantitation of six components: baicalin, berberine hydrochloride, quercetin, kaempferol, isorhamnetin and baicalein in intestinal perfusate using rotundin as an internal standard. The chromatographic separation was performed on a Welchrom‐C₁₈ column (250 × 4.6 mm i.d. with 5.0 µm particle size) with a mobile phase consisting of acetonitrile, water, phosphoric acid and triethylamine (30:70:0.2:0.1,v/v) at a flow rate of 1.0 mL/min and a UV detection at 270 nm. The method had a chromatographic run time of 30 min and excellent linear behavior over the investigated concentration ranges observed with the values of r higher than 0.99 for all the analytes. The lower limit of quantification of the analytical method was 0.09 µg/mL for berberine hydrochloride, quercetin, kaempferol and baicalein and 0.18 µg/mL for baicalin and isorhamnetin. The intra‐ and inter‐day precisions measured at three concentration levels were all less than 10% for all analytes. The bias ranged from ?6.91 to 4.33%. The validated method has been successfully applied to investigate the rat intestine absorption profiles of baicalin, berberine hydrochloride, quercetin, kaempferol, isorhamnetin and baicalein. Copyright © 2009 John Wiley & Sons, Ltd.     

Simultaneous determination of 11 fluorescent whitening agents in food‐contact paper and board by ion‐pairing high‐performance liquid chromatography with fluorescence detection

4,4′‐Diaminostilbene‐2,2′‐disulfonic acid based fluorescent whitening agents (DSD‐FWAs) are prohibited in food‐contact paper and board in many countries. In this work, a reliable high‐performance liquid chromatography method was developed for the simultaneous determination of 11 common DSD‐FWAs in paper material. Sample preparation and extraction as well as chromatographic separation of multicomponent DSD‐FWAs were successfully optimized. DSD‐FWAs in prepared samples were ultrasonically extracted with acetonitrile/water/triethylamine (40:60:1, v/v/v), separated on the C₁₈ column with the mobile phase containing tetrabutylammonium bromide, and then detected by a fluorescence detector. The limits of detection were 0.12–0.24 mg/kg, and the calibration curves showed the linear correlation (R² ≥ 0.9994) within the range of 8.0–100 ng/mL, which was equivalent to the range of 0.80–10 mg/kg in the sample. The average recoveries and the RSDs were 81–106% and 2–9% at two fortification levels (1.0 and 5.0 mg/kg) in paper bowls, respectively. The successful determination of 11 DSD‐FWAs in food‐contact paper and board obtained from local markets indicated that the newly developed method was rapid, accurate, and highly selective.     

Preconcentration and determination of ceftazidime in real samples using dispersive liquid–liquid microextraction and high‐performance liquid chromatography with the aid of experimental design

A rapid and simple method for the extraction and preconcentration of ceftazidime in aqueous samples has been developed using dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography analysis. The extraction parameters, such as the volume of extraction solvent and disperser solvent, salt effect, sample volume, centrifuge rate, centrifuge time, extraction time, and temperature in the dispersive liquid–liquid microextraction process, were studied and optimized with the experimental design methods. Firstly, for the preliminary screening of the parameters the taguchi design was used and then, the fractional factorial design was used for significant factors optimization. At the optimum conditions, the calibration curves for ceftazidime indicated good linearity over the range of 0.001–10 μg/mL with correlation coefficients higher than the 0.98, and the limits of detection were 0.13 and 0.17 ng/mL, for water and urine samples, respectively. The proposed method successfully employed to determine ceftazidime in water and urine samples and good agreement between the experimental data and predictive values has been achieved.     

Optimized determination of polybrominated diphenyl ethers by ultrasound‐assisted liquid–liquid extraction and high‐performance liquid chromatography

A method based on ultrasound‐assisted liquid–liquid extraction and high‐performance liquid chromatography has been optimized for the determination of six polybrominated diphenyl ether congeners. The optimal condition relevant to the extraction was first investigated, more than 98.7 ± 0.7% recovery was achieved with dichloromethane as extractant, 5 min extraction time, and three cycles of ultrasound‐assisted liquid–liquid extraction. Then multiple function was employed to optimize polybrominated diphenyl ether detection conditions with overall resolution and chromatography signal area as the responses. The condition chosen in this experiment was methanol/water 93:7 v/v, flow rate 0.80 mL/min, column temperature 30.0°C. The optimized technique revealed good linearity (R² > 0.9962 over a concentration range of 1–100 μg/L) and repeatability (relative standard deviation < 6.3%). Furthermore, the detection limit (S/N = 3) of the method were ranged from 0.02 to 0.13 μg/L and the quantification limit (S/N = 10) ranged from 0.07 to 0.35 μg/L. Finally, the proposed method was applied to spiked samples and satisfactory results were achieved. These results indicate that ultrasound‐assisted liquid–liquid extraction coupled with high‐performance liquid chromatography was effective to identify and quantify the complex polybrominated diphenyl ethers in effluent samples.     

Vortex‐assisted liquid–liquid micro‐extraction and high‐performance liquid chromatography for a higher sensitivity methyl methacrylate determination in biological matrices

A vortex‐assisted liquid–liquid micro‐extraction coupled with high‐performance liquid chromatography, with UV–vis, is proposed to pre‐concentrate methyl methacrylate and to improve separation in biological matrices. The use of 1‐octanol as extracting phase, its volume, the need for a dispersant agent, the agitation conditions and the cooling time before phase separation were evaluated. In optimum conditions, enrichment factors of 20 (±0.5) and enrichment recovery of 99% were obtained. The straightforward association of this extraction process with the HPLC method, previously regulated by the International Organization for Standardization, afforded a detection limit of 122 ng/mL and a quantification limit of 370 ng/mL. The within‐batch precision, relative standard deviation, was 3% for a sample with 1.49 µg/mL and 4% for a sample with 13.4 µg/mL. The results showed a between batch‐precision of 21% for experiments performed on five different days, for a sample with a concentration of 1.10 µg/mL in methyl methacrylate. Copyright © 2013 John Wiley & Sons, Ltd.     

Systematic evaluation and optimization of high‐performance liquid chromatography separation of polyoxins

The chromatographic behavior of a kind of nucleoside peptides, polyoxins, was investigated in this study. Molecular simulation technique was used to elucidate the temperature‐dependent peak sharpening of polyoxins. There was a relatively small energy barrier between the global minimum conformer and the local minimum conformer of polyoxin A and the high temperature helped to quickly cross the energy barrier and accelerate the conformational transformation for getting the global minimum, so that stationary phase could not identify these two conformations and presented a sharp peak. Two kinds of mixed‐mode columns, strong cation exchange or strong anion exchange ligands bonded with C18 (C18SCX and C18SAX) were used to improve separation selectivity of four polyoxins (A, K, F, H). The electrostatic attraction was necessary to increase the retention to ensure that the alkyl chain can give better play to its hydrophobic effect. Therefore, four polyoxins were well separated on C18SCX at pH 2 and they were also well separated on C18SAX at pH 7. In the small‐scale purification of polyoxins, the sample loading of the C18SCX was five times than that of the C18SAX and the purity of the collected four polyoxins was all over 90%.     

高效液相色谱法同时测定厚朴温中胶囊中的7种有效成分

建立了同时测定厚朴温中胶囊中山姜素、甘草酸、和厚朴酚、小豆蔻明、木香烃内酯、去氢木香内酯及厚朴酚含量的反相高效液相色谱法。固定相为Scienhome C18柱(250 mm×4.6 mm,5 μm),流动相为甲醇-乙腈-0.06%磷酸溶液(体积比为38∶27∶35),流速为1.0 mL/min,柱温为30 ℃,检测波长为235 nm。在上述条件下,山姜素、甘草酸、和厚朴酚、小豆蔻明、木香烃内酯、去氢木香内酯及厚朴酚的质量浓度分别在0.885～17.7,107～2140,8.85～17.7,1.035～20.7,4.85～97,5.9～118和17.5～350 mg/L时与色谱峰面积之间的线性关系良好;回收率分别为96.9%～101.1%,96.0%～100.5%,100.3%～100.8%,97.7%～101.4%,100.4%～102.3%,96.0%～102.3%和96.2%～100.6%。该方法简便、快速、准确,可用于厚朴温中胶囊的质量控制。     

Simultaneous determination of six synthetic phenolic antioxidants in edible oils using dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography with diode array detection

A simple, rapid, organic‐solvent‐ and sample‐saving pretreatment technique, called dispersive liquid–liquid microextraction, was developed for the determination of six synthetic phenolic antioxidants from edible oils before high‐performance liquid chromatography with diode array detection. The entire procedure was composed of a two‐step microextraction and a centrifugal process and could be finished in about 5 min, only consuming only 25 mg of sample and 1 mL of the organic solvent for each extraction. The influences of several important parameters on the microextraction efficiency were thoroughly investigated. Recovery assays for oil samples were spiked at three concentration levels, 50, 100 and 200 mg/kg, and provided recoveries in the 86.3–102.5% range with a relative standard deviation below 3.5%. The intra‐day and inter‐day precisions for the analysis were less than 3.8%. The proposed method was successfully applied for the determination of synthetic phenolic antioxidants in different oil samples, and satisfactory results were obtained. Thus, the developed method represents a viable alternative for the quality control of synthetic phenolic antioxidant concentrations in edible oils.     

Yttria‐based sol–gel coating for capillary microextraction online coupled to high‐performance liquid chromatography

This work about the development of yttria‐based polymeric coating using [bis(hydroxyethyl) amine] terminated polydimethylsiloxanes and yttrium trimethoxyethoxide inside the capillary. The coated capillary was utilized for online capillary microextraction and high‐performance liquid chromatography analysis. The prepared coating material was characterized using scanning electron microscopy, X‐ray photoelectron spectroscopy, energy dispersive X‐ray spectrometry, and thermogravimetric analysis. The coated capillary with polymer presented better extraction efficiency compared with the pure yttria‐based coated capillary with applicability in extreme pH environments (pH 0–pH 14). Excellent extraction towards polyaromatic hydrocarbons, aldehydes, ketones, alcohols, phenols, and amides was observed with limit of detection ranging from 0.18 to 7.35 ng/mL (S/N = 3) and reproducibility in between 0.6 and 6.8% (n = 3). Capillary‐to‐capillary extraction analysis has presented reproducibility between 4.1 and 9.9%. The analysis provided linear response for seven selected phenols in the range of 5–200 ng/mL with R² values between 0.9971 and 0.9998. The inter‐day, intra‐day, and capillary‐to‐capillary reproducibility for phenols was also <10%. Real sample analysis by spiking 5, 50, and 200 ng/mL of phenols in wastewater and pool‐water produced recovery between 84.7 and 94.3% and reproducibility within 7.6% (n = 3).     

Rapid pretreatment and determination of bisphenol A in water samples based on vortex‐assisted liquid–liquid microextraction followed by high‐performance liquid chromatography with fluorescence detection

A method for the rapid pretreatment and determination of bisphenol A in water samples based on vortex‐assisted liquid–liquid microextraction followed by high‐performance liquid chromatography with fluorescence detection was proposed in this paper. A simple apparatus consisting of a test tube and a cut‐glass dropper was designed and applied to collect the floating extraction drop in liquid–liquid microextraction when low‐density organic solvent was used as the extraction solvent. Solidification and melting steps that were tedious but necessary once the low‐density organic solvent used as extraction solvent could be avoided by using this apparatus. Bisphenol A was selected as model pollutant and vortex‐assisted liquid–liquid microextraction was employed to investigate the usefulness of the apparatus. High‐performance liquid chromatography with fluorescence detection was selected as the analytical tool for the detection of bisphenol A. The linear dynamic range was from 0.10 to 100 μg/L for bisphenol A, with good squared regression coefficient (r² = 0.9990). The relative standard deviation (n = 7) was 4.7% and the limit of detection was 0.02 μg/L. The proposed method had been applied to the determination of bisphenol A in natural water samples and was shown to be economical, fast, and convenient.     

Rapid determination of trace semicarbazide in flour products by high‐performance liquid chromatography based on a nucleophilic substitution reaction

Semicarbazide, a toxic food contaminant, widely exists in food products and it originates from the thermal degradation of a food additive of azodicarbonamide or a metabolite of nitrofurazone abused in meat specimens. Many previous methods for semicarbazide determination usually required expensive instruments, difficult‐to‐prepare monoclonal antibodies, and a long operation time. In this study, a high‐performance liquid chromatography method was developed for the rapid determination of trace semicarbazide coupling with a nucleophilic substitution reaction firstly using 4‐nitrobenzoyl chloride as derivatization reagent. The derivatization reaction was mild at room temperature for 1 min in neutral solution. Then, semicarbazide derivative was separated and quantified by high‐performance liquid chromatography with ultraviolet detection under optimal separation conditions at λ _max = 261 nm. The proposed method offered the detection limit of 1.8 μg/L and was successfully applied for the rapid determination of trace semicarbazide in flour products. Semicarbazide in positive real samples could be actually found and quantified in the range of 0.47−7.53 mg/kg. The recoveries were 76.6−119% with relative standard deviations of 0.5–9.1% (n = 3). This developed method was rapid, reliable, and convenient for the determination of trace semicarbazide in food.     

反相高效液相色谱法同时测定化妆品中7种萘二酚类物质

建立了反相高效液相色谱((RP-HPLC))同时测定化妆品中7种萘二酚类物质的分析方法。膏霜类、乳液类和水类样品用95%(v/v)乙醇提取,粉类样品用95%乙醇-0.1%乙酸(3:2, v/v)溶液提取,经离心、过滤后,用C18柱,以甲醇-0.1%乙酸溶液为流动相梯度洗脱分离,使用二极管阵列检测器检测,以保留时间定性,并以紫外吸收光谱图辅助定性,外标法定量。结果表明,萘二酚类物质在线性范围内线性关系良好,相关系数均不低于0.999 0,方法的定量限(以信噪比为10计)为0.5～1.2 mg/kg,添加水平为5.0～50 mg/kg时回收率为84.0%～102%,相对标准偏差(n=6)为1.3%～5.7%。该法前处理简单、回收率高、精密度好,适用于非蜡基类化妆品中萘二酚类物质的测定。     

Simultaneous separation and determination of thallium in water samples by high‐performance liquid chromatography with inductively coupled plasma mass spectrometry

An analytical method for separation and determination of thallium species in water using high‐performance liquid chromatography with inductively coupled plasma mass spectrometry was developed. The composition and concentration of mobile phase, injection volume, and pH value were optimized respectively with an anion or cation exchange column. The results showed that Tl(I) and Tl(III) were effectively separated using anion exchange column Hamilton PRP‐X100, with the mobile phase consisting of 200 mmol/L ammonium acetate and 10 mmol/L diethylenetriaminepentaacetic acid (pH = 4.2). When using a Dionex cation exchange guard column, CS12A, 15 mmol/L HNO₃, and 3 mmol/L diethylenetriaminepentaacetic acid as the mobile phase, Tl(I) and Tl(III) could be effectively separated. The detection limits of the methods were 3–6 and 9–12 ng/L, respectively. In a solution containing Fe ions and oxalic acid, a significant quantity of Tl(I) was oxidized. Fe ions and oxalic acid in the water samples did not interfere with high‐performance liquid chromatography‐inductively coupled plasma mass spectrometry measurement results.     

Ultrasound‐assisted magnetic dispersive solid‐phase microextraction: A novel approach for the rapid and efficient microextraction of naproxen and ibuprofen employing experimental design with high‐performance liquid chromatography

A simple, rapid, and sensitive method for the determination of naproxen and ibuprofen in complex biological and water matrices (cow milk, human urine, river, and well water samples) has been developed using ultrasound‐assisted magnetic dispersive solid‐phase microextraction. Magnetic ethylendiamine‐functionalized graphene oxide nanocomposite was synthesized and used as a novel adsorbent for the microextraction process and showed great adsorptive ability toward these analytes. Different parameters affecting the microextraction were optimized with the aid of the experimental design approach. A Plackett–Burman screening design was used to study the main variables affecting the microextraction process, and the Box–Behnken optimization design was used to optimize the previously selected variables for extraction of naproxen and ibuprofen. The optimized technique provides good repeatability (relative standard deviations of the intraday precision 3.1 and 3.3, interday precision of 5.6 and 6.1%), linearity (0.1–500 and 0.3–650 ng/mL), low limits of detection (0.03 and 0.1 ng/mL), and a high enrichment factor (168 and 146) for naproxen and ibuprofen, respectively. The proposed method can be successfully applied in routine analysis for determination of naproxen and ibuprofen in cow milk, human urine, and real water samples.     

Simultaneous preconcentration and determination of 2,4‐D,alachlor and atrazine in aqueous samples using dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography ultraviolet detection

Dispersive liquid–liquid microextraction coupled with high‐performance liquid chromatography‐ultraviolet detection as a fast and inexpensive technique was applied to the simultaneous extraction and determination of traces of three common herbicides, 2,4‐D, alachlor and atrazine, in aqueous samples. The critical experimental parameters, including type of the extraction and disperser solvents as well as their volumes, sample pH, salt addition, extraction time and centrifuging time, and speed were investigated and optimized. Under the optimum conditions, the calibration graphs found to be linear in the range of 0.3–200 μg/L with limits of detection in the range of 0.05–0.1 μg/L. The relative standard deviations were in the range of 4.5–6.2% (n = 7). The relative recoveries of well, tap, and river water samples which have been spiked with different levels of herbicides were 92.0–107.0, 82.0–104.0, and 82.0–86.0%, respectively.     

An environmentally friendly sodium dodecyl sulfate‐synergistic microwave‐assisted extraction followed by ultra‐high‐performance liquid chromatography with photodiode array method for the simultaneous extraction and determination of iridoids,phenylpropanoids, and lignans from Eucommiae Cortex

A simple and green sodium dodecyl sulfate‐synergistic microwave‐assisted extraction method was developed to extract and determine the iridoids, phenylpropanoids, and lignans in Eucommiae Cortex followed by ultra‐high‐performance liquid chromatography with photodiode array detection. The biodegradable solution (sodium dodecyl sulfate) was used as a promising alternative to organic solvents. The response surface methodology provided the optimum extraction conditions (2 mg/mL sodium dodecyl sulfate, 1100 W microwave power, and 6 min extraction time). The recoveries of three types of components ranged from 95.0 to 105% (RSDs < 5%). The intra‐ and inter‐day precision and accuracy were less than 3.40% and within the range of 97.1‐105%, respectively. Compared with other extraction methods, this newly established method was more efficient and environmental friendly. The results demonstrated that sodium dodecyl sulfate‐synergistic microwave‐assisted extraction followed by ultra‐high‐performance liquid chromatography with photodiode array method was applicable for the simultaneous extraction and determination of these three types of compounds for quality evaluation of Eucommiae Cortex.     

Ultrasound‐assisted dispersive micro‐solid‐phase extraction based on N‐doped mesoporous carbon and high‐performance liquid chromatographic determination of 1‐hydroxypyrene in urine samples

In this research, a new ultrasound‐assisted dispersive micro‐solid‐phase extraction method based on N‐doped mesoporous carbon sorbent followed by high‐performance liquid chromatography equipped with diode array detector for trace measurement of 1‐hydroxypyrene as a metabolite of exposure to polycyclic aromatic hydrocarbons was optimized. Herein, the hard template method was used for the preparation of N‐doped mesoporous carbon sorbent. The prepared sorbent was characterized using the Brunauer–Emmett–Teller method, transmission electron microscopy, and elemental analysis. Parameters affecting the extraction of the target metabolite were investigated using the Box–Behnken design method. Considering optimum parameters, the plotted calibration curve for 1‐hydroxypyrene was linearly correlated with the concentration span of 0.1–50 μg/L for urine media. The accuracy of the optimized procedure was examined through the relative recovery tests on the fortified urine specimens. The relative recoveries fell between 95 and 101%. The method detection limit of the proposed procedure was also calculated to be 0.03 μg/L.